This application relates to subject matter which is similar to that of applicant""s U.S. Pat. Nos. 6,001,950 of Dec. 14, 1999 and 6,140,420 of Oct. 31, 2000 but the polyphenolics (condensates) and epoxy derivatives of this invention show an unexpected higher increase in fluorescence as compared to that of the prior patents while, at the same time, showing a high ultraviolet (UV) absorbance.
Polyphenolics, such as those prepared from the condensation of glyoxal and a molar excess of a phenolic monomer such as phenol itself in the presence of an acid catalyst, find utility in the same manner as other polyphenolics and particularly for preparing epoxidized polyphenolics which can be used for coatings and electronic applications as well as adhesives and laminates in the production of printed circuit boards.
Glyoxal-phenolic condensates contain a variety of compounds, including polyphenolics such as di-, tri-, tetraphenolics and higher polyphenolics. When the reactants are phenol itself and glyoxal, the polyphenol is a mixture wherein the predominant tetraphenolic compound is tetrakis(4-hydroxyphenyl)ethane (TPE) which is also referred to as 1, 1, 2, 2-tetrakis(4-hydroxyphenyl)ethane. Glycidylation of the tetrakis(4-hydroxyphenyl)ethane gives the tetraglycidyl ether of tetrakis(4-hydroxyphenyl)ethane. The polyphenolics of this invention will typically contain less than about 6%, preferably less than 4% and particularly less than about 2% or 3% such as less than 1% of TPE.
The condensates and epoxy derivatives of this invention are particularly useful for measurement of fluorescence and/or UV absorbance when automatic optical inspection (AOI) is used for quality control such as in the manufacture of laminates. They can be used alone, after epoxidation, as adducts with epoxy resins, adducts of epoxidized condensates with phenolic novolacs, or in blends with conventional phenolic novolacs and/or prior art glyoxal phenolic condensates such as those of U.S. Pat. No. 6,001,950 which do not have the high fluorescence of this invention. High UV absorbance is desirable for the manufacture of laminates used in electronic applications such as high density multilayer printed circuit boards.
Applicant has found process conditions and the use of oxalic acid as catalyst for obtaining polyphenolics, epoxy derivatives, and compositions containing the foregoing which have unexpectedly high fluorescence with a relatively high UV absorbance. The fluorescence is substantially higher than glyoxal-phenolic condensates prepared by other methods and catalysts within the wavelengths generally used for AOI quality control. Photoimageable materials can be used in conjunction with these condensates.
In this invention, polyphenolics can be obtained with the desirable optical properties, and depending on the method used in making the polyphenolic, one or more additional desirable properties such as: (a) preparation of an essentially metal ion-free polyphenolic without recourse to catalyst filtration or neutralization and water washing steps wherein recovery of phenolic monomer is simplified and the reactor yield is increased in those cases where the catalyst is not neutralized with a metal ion; (b) preparation of polyphenolics with increased solubility in organic solvents; (c) performance of the condensation with a single addition of glyoxal and a single vacuum distillation whereas some other methods use multiple glyoxal additions and vacuum distillations; or the level of tetra(4-hydroxyphenyl)ethane can be unexpectedly low.
The phrase xe2x80x9caldehyde equivalentsxe2x80x9d as used in this application refers to aldehyde in the glyoxal charged or remaining in the reaction mixture or product when measured by the below described method. Such measurements are reported in aldehyde equivalents reacted in comparison with the aldehyde equivalents charged to the reaction mixture. Thus, if measurements of aldehyde equivalents of the glyoxal charged to the reactor show a total of X aldehyde equivalents and measurements after reaction in the reaction mixture later show aldehyde equivalents of xc2xd of X, then the aldehyde equivalents reacted are 50% of that charged. Certain ketone groups, referred to as xe2x80x9creactive ketonesxe2x80x9d are also measured by the below test method. The ketone groups may be formed during the condensation reaction and these are included in measuring of the aldehyde equivalents and are considered as part of the aldehyde equivalents herein. The term xe2x80x9creactive ketonexe2x80x9d is used to describe those ketones which affect the per cent of aldehyde equivalents.
The method for determining aldehyde equivalents is by taking 1.0 gram of reaction mixture and diluting it with 50 ml of methanol. The pH is then adjusted to 3.5 with dilute sodium hydroxide. There is then added, to the pH adjusted sample, 25 ml of 10% aqueous hydroxylamine hydrochloride with stirring. The sample is stirred for 10 minutes and then the sample is back titrated with 0.25 Normal (N) sodium hydroxide to pH of 3.5. The number of milliliters (mis) (the titre) of the sodium hydroxide solution used to back titrate the sample to a pH of 3.5 is used to calculate the aldehyde equivalents.
The aldehyde equivalents for the sample are then calculated by the following formula: (2.9 times 0.25 times (mis sodium hydroxide titre).The value obtained by this formula is then compared to the aldehyde equivalents obtained by the above method and formula based on one gram of an unheated mixture of phenolic monomer and glyoxal in the weight ratio of glyoxal to phenolic monomer used until that time or the time in question, after correcting for water which may have been added or remove, e.g., by distillation, in order to determine the percent aldehyde equivalents reacted.
Apart from the above method for determining aldehyde equivalents, the aldehyde groups of the starting glyoxal can simply be compared with the aldehyde groups and reactive ketone groups in the reaction mixture or product to determine the amount of aldehyde and reactive ketone groups reacted. In making the percentage calculations, adjustments again need to be made for the addition or removal of water and the weight ratio of phenolic monomer to gyloxal used at the time in question as compared to that of the initial mixture containing the unreacted glyoxal, keeping in mind that each molecule of glyoxal has two aldehyde groups.
Unless otherwise indicated, the fluorescence measurements herein are based on the maximum counts for a 0.05% solution of the polyphenolic or derivative thereof, dissolved in tetrahydrofuran (THF) at an excitation wave length of 442 nm (nanometers) when measured within the range of about 450 to 650 nm. Although the range of 450 to 650 was measured, the maximum counts for the products of this invention occurs at the 525-535 nm range. It is the maximum counts that are compared in the measurements given in this application. The time for measurement of the maximum counts and the time during which the excitation is measured, such excitation time also referred to as xe2x80x9cacquisition timexe2x80x9d, are the same and in the measurements in this application such time was either one-half second or one second.
When the polyphenolic or derivative thereof is compared with Acridine Orange Base which was purchased from the Aldrich Chemical Company, all experimental conditions are the same except that the Acridine Orange Base is diluted and measured at a concentration of 0.31 mg/liter (milligrams per liter) dissolved in methanol. This concentration of Acridine Orange Base gives about the same amount of fluorescence as that of a 0.05% by weight solution in THF for the resin of Example 7 in applicant""s U.S. Pat. No. 6,001,950.
The Acridine Orange Base itself is a solution containing about 75% of the dye when sold by the Aldrich Chemical Co. of Milwaukee, Wis. The Acridine Orange base of Aldrich Chemical Company is described on page 33 of the Aldrich Chemical Company catalogue which is dated 2000-2001. The instrument used to make the measurements is a CM 1000 instrument. CM 1000 refers to Cure Monitor 1000 which is an instrument made by Spectra Group Ltd., Inc. of Maumee, Ohio. Acquisition time is the exposure time at the designated wavelength. A count is a basic unit used by a large number of light measuring devices for data output and refers to a process of digitization of accumulated signal. In the case of a CCD detector that is used by Spectra Group Limited, Inc. of Maumee, Ohio and which was used for the data set forth herein, light produces an electrical charge on the detector that is subsequently read out by a digitizer. The digitizer is set to record one count for approximately every 10 units of charge (electrons) it reads.
The UV absorbance values of this invention are obtained from samples of the polyphenolic or derivatives thereof prepared by dissolving the material in question at a concentration of 0.020 g (grams) per 200 ml (milliliters) of THF (tetrahydrofuran) and the absorbance measurement made at 350 nm (nanometers) or 365 nm.
In one aspect, this invention relates to polyphenolics having a fluorescence of at least 30% higher, preferably at least 50% higher and particularly at least 80% higher than that of applicant""s Example 7 of U.S. Pat. No. 6,001,950. The concentration of the Acridine Orange Base purchased from Aldrich Chemical Co. was diluted with methanol to 0.31 mg/liter for the work in this application so that it would have the same fluorescence intensity as Example 7 of the above 950 patent.
In another aspect, this invention relates to polyphenolics of a phenolic monomer and glyoxal wherein the polyphenolic has an ultraviolet absorbance of at least about 0.400 at 350 nm and/or at least about 0.220 at 365 nm and a minimum fluorescence as set forth in the above paragraph. Preferably, the polyphenolic of this invention will have an ultraviolet absorbance of at least about 0.500 at 350 nm and at least 0.300 at 365 nm which is much the same as that of the 950 patent.
In yet other aspects, this invention is directed to the polyphenolics of this invention, epoxidized products prepared therefrom, compositions containing the polyphenolics or epoxidized derivatives thereof and compositions with other phenolic novolacs and/or epoxidized derivatives thereof.
In still another aspect, this invention is directed to laminates comprising the novel polyphenolics, epoxidized derivatives and compositions thereof as well as the method for the manufacture of such laminates.
In a further aspect, this invention relates to methods for preparing the polyphenolic products of this invention.
The Phenolic Monomer
The phenolic monomer is phenol itself or optionally wherein up to 20 mole percent of the phenol is replaced by another monocyclic-monohydric phenolic monomer having from 7 to 9 carbon atoms. When such other phenolic monomer is used together with phenol itself, such phenolic monomer is generally used in a quantity of from about 5 mole percent to about 20 mole percent of the total phenolic monomer charge. The terms xe2x80x9cglyoxal-phenolic condensatexe2x80x9d, xe2x80x9cpolyphenolicsxe2x80x9d or simply xe2x80x9ccondensatexe2x80x9d are used herein to describe both the glyoxal-phenol as well as that wherein up to 20% of the phenol has been replaced with another phenolic monomer. Illustrative of the other monocyclic-monohydric phenolic monomers there can be mentioned those having alkyl or alkoxy groups of 1 to 3 carbon atoms substituted in the para, ortho, or meta position of the monocyclic-monohydric phenolic and mixtures thereof. Preferred monocyclic-monohydric phenolics include 3-methylphenol, 3-ethylphenol, 3-methoxyphenol and 3-ethoxyphenol. It is preferred that the glyoxal-phenolic condensate be that of glyoxal and phenol itself or phenol wherein not more than about 10 mole % of the phenol is replaced by another phenolic monomer.
The Glyoxal Reactant
The glyoxal reactant can be in various forms such as relatively pure monomeric glyoxal, polymerized glyoxal or glyoxal dissolved in water. Illustratively, glyoxal is normally used as a 30% to 60% by weight solution of glyoxal in water and particularly a 40% solution in water.
The Acid Catalyst
The acid catalyst used in this invention for the condensation reaction of a phenolic monomer and glyoxal is oxalic acid. Such catalyst can be removed from the reaction mixture by distilling the reaction mixture at a temperature above about 140xc2x0 C.
Oxalic acid can be used in its various forms such as the pure compound, the dihydrate, or mixtures thereof, all of which are referred to as oxalic acid herein. The oxalic acid catalyst is decomposed to volatile components at the temperatures above about 140xc2x0 C.
The polyphenols of this invention can be prepared by two different methods.
Preparation of the Glyoxal-Phenolic Condensates by the First Method
In the first method for making the glyoxal-phenolic condensates (polyphenolics) of this invention, glyoxal is added to phenol while the phenol is at a temperature of about 110xc2x0 C. to about 140xc2x0 C. to form a reaction mixture while distilling off water. Up to 20 mole % of another monocyclic and monohydric phenolic monomer wherein such monomer has 7 to 9 carbon atoms can replace a portion of the phenol. The reaction is conducted in the presence of about 0.5% to 4% of oxalic acid as catalyst based on the total weight of phenol or phenol with said another phenolic monomer. The molar ratio of the total amount of glyoxal to phenol or phenol together with said another phenolic monomer can vary from about 0.15 to 0.25. The reaction at a temperature of about 110xc2x0 C. to about 140xc2x0 C. and distillation of water is continued until at least about 85% of the aldehyde equivalents of the glyoxal have reacted.
The Reaction Conditions for Preparation of the Glyoxal-Phenolic Condensates by the First Method
The glyoxal is added to the phenolic monomer, i.e., phenol or phenol with another phenolic monomer, while the phenolic monomer or mixture thereof is heated within a temperature range of about 110xc2x0 C. to about 140xc2x0 C. and preferably about 120xc2x0 C. to about 130xc2x0 C. The oxalic acid catalyst is preferably present in the heated phenolic monomer at the time the glyoxal is added. Water is distilled out of the reaction mixture while the glyoxal is being added. The glyoxal is added at a rate which does not bring the temperature of the reaction mixture down below about 110xc2x0 C. Illustratively, the glyoxal addition typically takes about 1 to 3 hours.
The molar ratio of glyoxal to phenolic (phenol or phenol plus other phenolic monomer) in making the glyoxal-phenolic condensates by the first method of this invention is from about 0.15 to 0.25 moles of glyoxal for each mole of phenolic charged and preferably about 0.16 to 0.23 moles of glyoxal for each mole of phenolic charged. Total mole ratios of less than about 0.15 moles of glyoxal for each mole of phenolic charged give more of the tetraphenolics, such as TPE which is essentially devoid of ultraviolet absorbance in the ranges given above for AOI quality control. Ratios of greater than about 0.25 or 0.27 moles of glyoxal for each mole of phenolic monomer lead to longer reaction times and are likely to give product with higher viscosity.
The total time for the condensation reaction of aldehyde with the phenolic monomer prior to removal of catalyst or cooling of the reaction mixture will typically vary from about 6 to about 14 hours and preferably about 7 to about 10 hours.
Preparation of the Glyoxal-Phenolic Condensate by the Second Method
In the method for making the glyoxal-phenolic condensates of this invention by the second method, glyoxal is reacted with phenol in a molar ratio of about 0.15 to about 0.27 moles of glyoxal for each mole of phenol or phenol together with another monocyclic and monohydric phenolic monomer wherein such phenolic monomer has from 7 to 9 carbon atoms and wherein a total quantity of from about 0.5% to about 4% by weight of oxalic acid as the catalyst is used in the method, the quantity of catalyst being based on the weight of phenol or phenol together with the said another phenolic monomer, said method comprising the steps of:
(A) heating and distilling water under vacuum out of a mixture at a temperature of about 55xc2x0 C. to about 90xc2x0 C. wherein the mixture comprises substantially all of the glyoxal to be charged in the reaction, phenol and at least 5% by weight of water and wherein the quantity of phenol is from about 5% to about 20% by weight of the total phenolic monomer to be charged in the reaction;
(B) continuing the heating and distillation of water, preferably under vacuum, from the mixture until the amount of water in the mixture is from about 5% to 30% by weight of the mixture;
(C) adding a quantity of from about 0.2% to about 1% of oxalic acid to the mixture to form a reaction mixture in a reactor, said quantity of oxalic acid based on the total quantity of phenolic monomer to be charged in the reaction, heating the reaction mixture at a temperature within the range of about 800 C to 125xc2x0 C. until from about 15% to about 40% of aldehyde equivalents or aldehyde groups and reactive ketone groups have reacted;
(D) adding the remainder of the oxalic acid and phenol wherein optionally up to about 20 mole % of the phenol to be charged to the reactor is replaced with another monocyclic and monohydric phenolic monomer, said monomer having from 7 to 9 carbon atoms, and heating the reaction mixture at a temperature in the range of about 105xc2x0 C. to about 135xc2x0 C. until at least a total of 85% of the aldehyde equivalents or aldehyde groups and reactive ketone groups have reacted.
In a modification of the second method a glyoxal-phenolic condensate is prepared by adding substantially all of the glyoxal and from about 5% to about 20% of phenol by weight of the total quantity of phenolic monomer to be charged to a reactor and about 0.2% to about 1% of oxalic acid, based on the weight of the total quantity of phenolic monomer to be charged in the reactor, to form a reaction mixture wherein the reaction mixture contains from about 10% to 30% by weight of water; heating the reaction mixture at a temperature of within the range of about 80xc2x0 C. to 125xc2x0 C. until about 15% to about 40% of the aldehyde equivalents or aldehyde groups and reactive ketone groups have reacted; adding the remainder of the oxalic acid and phenolic monomer wherein said phenolic monomer is phenol or phenol with another monocyclic and monohydroxy phenolic monomer, the said another phenolic monomer having from 7 to 9 carbon atoms, the quantity of said another phenolic monomer being up to 20 mole % of the total quantity of phenolic monomer to be charged to the reactor; and heating the reaction mixture at a temperature in the range of about 105xc2x0 C. to about 135xc2x0 C. until at lest 85% of the aldehyde equivalents or aldehyde groups and reactive ketone groups have reacted.
The water in the initial reaction mixture of the second method is generally at least about 5% to about 30% and preferably 10% to 20% by weight of the reaction mixture. However, the quantity of water can be substantially higher, e.g., 60% or more but it then should be distilled out of the mixture before any catalyst is added to get it down to a concentration of about 5% to 30% and preferably about 10% to 20% by weight of the reaction mixture. Typically, the water is present due to the glyoxal being used as an aqueous solution.
Reaction Conditions and Modifications for the Second Method
The molar ratio of glyoxal to phenolic (phenol or phenol plus other phenolic monomer) in the manufacture of the glyoxal-phenolic condensates by the second method is from about 0.15 to 0.27 moles of glyoxal for each mole of phenolic monomer and preferably about 0.16 to 0.25 moles of glyoxal for each mole of phenolic monomer charged to the reactor. Total mole ratios of less than about 0.15 moles of glyoxal for each mole of phenolic charged give more of the tetraphenolics, such as TPE which is essentially devoid of optical properties in the ranges given above for AOI quality control. Ratios of greater than about 0.27 moles of glyoxal for each mole of phenolic monomer lead to longer reaction times and are likely to give product with higher viscosity.
Initially, in the modification of the second method for making the polyphenolics of this invention, substantially all of the glyoxal is mixed with only about 5% to about 20% and preferably about 7% to 15% of phenol based on the total weight of the phenolic monomer to be charged to the reactor. Due particularly to the usual sale of glyoxal as an aqueous solution, the amount of water in the reaction is often above 30%. To remove water, to the 30% level or less, the mixture of phenol, glyoxal and water is heated at a temperature in the range of about 550 C to about 90xc2x0 C. and preferably about 60xc2x0 C. to about 80xc2x0 C. together with the application of vacuum to distill excess water out of the mixture. However, this step for the removal of water can be omitted if the mixture contains less than about 30% of water and phenol need not be mixed with the glyoxal in the distillation of water to arrive at the requisite quantity of water even when the mixture contains more than about 30% by weight of water. In this regard, it is believed that the only purpose for the distillation of water to bring the water content of the initial mixture to 30% or less is for increasing the speed of reaction. The phenol in the mixture of phenol with the aqueous glyoxal solution for the distillation of water acts as a diluent and helps to keep the glyoxal fluid.
A portion of the oxalic acid catalyst is added to the mixture in the above modification when the water content in the mixture is less than 30%. The portion of catalyst added at this stage is from about 0.2% to about 1% and preferably about 0.4% to about 1% based on the total quantity of phenolic monomer to be charged to the reactor. The reaction mixture which now contains a portion of the catalyst is heated at a temperature of about 80xc2x0 C. to about 125xc2x0 C. and preferably about 110xc2x0 C. to about 120xc2x0 C. Heating is continued until about 15% to about 40% and preferably about 20% to about 30% of the aldehyde equivalents or aldehyde groups and reactive ketone groups have reacted.
After reaction of about 15% to 40% of the aldehyde equivalents or aldehyde groups and reactive ketone groups, in the above modification, the remainder of the catalyst and phenolic monomer are added to the reaction mixture. The phenolic monomer is phenol or phenol having up to 20 mole % of the phenolic monomer to be charged to the reaction mixture replaced with a phenolic monomer other than phenol.
After addition of the remaining catalyst and phenolic monomer, in the above modification, the reaction mixture is again heated in the range of about 105xc2x0 C. to about 135xc2x0 C. and preferably about 110xc2x0 C. to about 130xc2x0 C. until at least 85%, preferably at least 90% and particularly at least 95% of the aldehyde equivalents or aldehyde groups and reactive ketone groups have reacted.
In the second method and its modification, the total time for the condensation reaction of aldehyde with the phenolic monomer up to the time of having at least 85% of aldehyde equivalents or aldehyde groups and reactive ketone groups reacted will typically vary from about 5 to about 15 hours and preferably about 7 to about 12 hours.
In both the First and Second Methods for Preparation of the Glyoxal-Phenolic Condensates
When the reaction temperature for preparation of the polyphenols is less than about 120xc2x0 C., distillation under vacuum may be used to remove water. Also, water is distilled off during the removal of catalyst or even during the removal of unreacted phenolic monomer.
The temperature for removal of the oxalic acid catalyst by distillation is generally above 140xc2x0 C. but less than about 170xc2x0 C. The temperature is raised above 140xc2x0 C. to about 170xc2x0 C., particularly about 155xc2x0 C. to about 160xc2x0 C. for removal, generally by decomposition and subsequent distillation of decomposition products of the oxalic acid. However, the temperature can be raised up to about 200xc2x0 C. to remove the catalyst and, under vacuum distillation, to also remove unreacted phenolic monomer.
The catalyst is preferably removed from the reaction mixture after at least about 85% of the aldehyde equivalents or aldehyde units and reactive ketone units of the total aldehyde equivalents or simply aldehyde units and reactive ketone units have reacted, and preferably when at least about 90% and particularly 93% of such aldehyde equivalents or said units have reacted. However, after the requisite reaction, e.g., after at least 85% of the aldehyde groups have reacted, the reaction mixture can be cooled and stored even though it can still contain water, catalyst and free or unreacted phenolic monomer. At this stage, the reaction mixture can also be referred to as a glyoxal-phenolic raw condensate. The glyoxal-phenolic raw condensate can then be heated to a temperature up to about 200xc2x0 C., preferably under vacuum, to prepare the glyoxal-phenolic condensate by removing the remaining water, oxalic acid catalyst and all but about 5% or less of free unreacted phenolic monomer.
All or substantially all of the water is removed from the reaction mixture when the catalyst is removed from the reaction mixture. Any water remaining in the reaction mixture after elimination of the catalyst can be removed by the distillation for removal of unreacted phenolic monomer.
After removal of water and the oxalic acid catalyst, unreacted (free) phenolic monomer is generally removed from the reaction mixture so as to bring the free phenolic monomer content of the reaction mixture to less than about 5%, preferably to less than about 2% and particularly less than about 1% by weight of the reaction mixture.
Removal of the unreacted phenolic monomer is attained by conventional means such as in the removal of unreacted phenol in novolac resins, e.g., flash distillation by heating the reaction mixture at an elevated temperature under vacuum. Thus, the temperature can be up to about 195xc2x0 C. or 200xc2x0 C. under about 25 to 30 inches of mercury vacuum. Steam sparging under vacuum at such temperatures can also be used to remove unreacted phenolic monomer from the product.
Concurrently with removal of the phenolic monomer, e.g., phenol, or as a separate step following removal of the catalyst, the reaction mixture is optionally heated at a temperature of from about 170xc2x0 C. to about 200xc2x0 C., preferably under vacuum, and particularly from about 180xc2x0 C. to about 195xc2x0 C. under vacuum. Such heating is conducted for a period of about 0.25 to 3 hours and preferably for about 0.5 to 2 hours. Heating at a temperature of about 170xc2x0 C. or 175xc2x0 C. to about 200xc2x0 C. for about 0.25 to 3 hours generally increases the fluorescence value of the polyphenolic. All or a portion of such heating can be conducted at the time the phenolic monomer is removed under vacuum. Optionally, the polyphenolic with 5% or less of unreacted phenolic monomer can be sparged with an inert gas and heated in the range of about 170xc2x0 or 175xc2x0 C. to 200xc2x0 C., preferably under vacuum, for about 0.5 to 3 hours. Illustrative of an inert gas there can be mentioned nitrogen or argon. The polyphenolic product is eventually cooled and generally comminuted, e.g., flaked.
The Glyoxal-Phenolic Condensate by the First Method
Properties of the glyoxal-phenolic condensate produced by the above described first method are as follows:
Fluorescence: The fluorescence of the glyoxal-phenolic condensate by the first method of preparation of this invention is at least about 50% higher and preferably at least 80% higher as compared to the Acridine Orange Base, under the conditions of measurement hereinabove set forth.
The glycidylated glyoxal-phenolic condensates of the first method of this invention will have a fluorescence which is at least 30% higher and preferably at least 40% higher than that of Acridine Orange Base under the conditions of measurement hereinabove set forth. Also, the glycidylated glyoxal-phenolic condensate of the first method has an ultraviolet (UV) absorbance at 350 nm of at lest 0.300 and preferably at least 0.350 and/or a UV absorbance at 365 nm of at least 0.180 and preferably at least 0.200 by the method given hereinabove.
The Glyoxal-Phenolic Condensate by the Second Method
Properties of the glyoxal-phenolic condensate by the second method are as follows:
Fluorescence of the polyphenolic product produced by the second method is at least about 30% higher and preferably at least 35% higher than Acridine Orange Base under the conditions set forth hereinbefore.
The glycidylated glyoxal-phenolic condensates prepared by the second method of this invention will have a fluorescence which is at least equal and preferably at least 20% higher than that of Acridine Orange Base under the conditions of measurement hereinabove set forth. The glycidylated glyoxal-phenolic condensates of this invention by the second method will have an ultraviolet (UV) absorbance at 350 nm of at least 0.300 and preferably at least 0.350 and/or a UV absorbance at 365 nm of at least 0.180 and preferably at least 0.200 by the method of measuring given hereinabove.
Preparation of Polyepoxides
The epoxidized products prepared from the polyphenolics (glyoxal-phenolic condensates) of this invention carry over with them the higher fluorescence and UV values of the polyphenolics although the quantity of polyphenolic and hence these optical properties are reduced due to the dilution of the polyphenolic portion of the epoxidized products.
Epoxidized products of the polyphenolics of this invention can be prepared by at least two different conventional routes. One route is by reaction of the glyoxal-phenolic condensate with a halohydrin in the presence of an alkali metal hydroxide to form glycidyl ethers of the polyphenolic. Such epoxidized products will typically have epoxy equivalent weights of about 190 to 230 and preferably about 205 to 225. Another route is by reacting a molar excess of a preformed polyfunctional epoxy with the glyoxal-phenolic condensate. Such epoxidized products by the latter route will typically have epoxy equivalent weights (WPE) of about 140 to 250 and preferably about 160 to 230.
In the first route for preparation of the polyepoxide, the polyepoxide is prepared by contacting the glyoxal-phenolic condensate with an excess of epichlorohydrin in the presence of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide at a temperature within the range of about 50xc2x0 C. to about 80xc2x0 C. Optional catalysts, such as quaternary ammonium salts, may be employed. The reaction can be carried out in the presence of an inert solvent, including alcohols such as ethanol, isopropanol, methyl isobutyl ketone (MIBK), toluene, ethers, and mixtures thereof.
Another method for preparing the polyepoxide by the first route is set forth in U.S. Pat. No. 4,518,762 of May 21, 1985 to Ciba Geigy Corp. which is incorporated herein by reference in its entirety. Briefly, in this process, the polyphenolic, preferably the glyoxal-phenolic purified product, is reacted at a temperature of 40xc2x0 to 100xc2x0 C., in the absence of any catalyst specific for the formation of the chlorohydrin ether intermediate, in the presence of 2 to 25% by weight, based on the reaction mixture, of a lower alkanol or lower alkoxyalkanol cosolvent, with excess epichlorohydrin, based on the phenolic hydroxy value, in the presence of 0.5 to 8% by weight of water, based on the reaction mixture, and with 0.9 to 1.15 equivalents of solid alkali metal hydroxide per phenolic hydroxyl group to give the epoxy derivative of the polyphenolic and wherein there is 0.5% to 8% by weight of water in the reaction mixture throughout the reaction period, using a solid alkali metal hydroxide in the form of beads of about 1 mm diameter, which hydroxide is charged to the reaction mixture portionwise or continuously during a gradually escalating addition program, and then isolating the epoxy novolac resin.
In the route for preparation of the epoxy resins which involves reacting a molar excess of a preformed polyfunctional epoxy with the glyoxal-phenolic condensate, one part by weight of such condensate is reacted with about 4 to about 8 parts of a polyepoxide at about 100xc2x0 C. to about 150xc2x0 C. using a catalyst, e.g., potassium hydroxide, benzyldimethylamine, benzyltrimethylammonium hydroxide, 2-methyl imidazole, and 2,4,6-tris(dimethylaminomethyl)phenol. Typical catalyst levels are about 0.1% to about 0.6% based on the reaction mass. Typical polyepoxides for reaction with the polyphenolic of this invention are those of diglycidyl ether resins, e.g., the diglycidyl ether resins of: bisphenol A; bisphenol F; resorcinol; neopentyl glycol; cyclohexane dimethanol; and mixtures thereof.
The polyphenolics of this invention can also be partially epoxidized without sacrifice in the desirable optical properties by reduction of the quantity of alkali used in the reaction with epichlorohydrin. Illustratively, reduction of caustic to about 40% to 70% of that in the methods of the above described first route affords partially epoxidized derivatives.
The term xe2x80x9cresiduexe2x80x9d or xe2x80x9cresiduesxe2x80x9d of a glyoxal-phenolic condensate refers to the glyoxal-phenolic derivative portion of a reaction product, e.g., in reaction with an epoxy resin. The quantity of residue is the amount of glyoxal-phenolic condensate of this 15 invention used in making a reaction product such as a resin or compound. Illustratively, if 10 grams of a glyoxal-phenolic condensate is reacted with 40 grams of an epoxide, the glyoxal-phenolic condensate residue of the composition would be 10 grams. Also, if 20 grams of a glyoxal-phenolic condensate is glycidylated and the glycidylated product is subsequently reacted with a phenol-formaldehyde novolac, the glyoxal-phenolic residue would still be 20 grams.
Unless the context indicates otherwise, the polyphenolics and various resins of this invention, e.g., epoxy resin derivatives thereof (including the glycidylated polyphenolics) and phenol novolacs are reactive, curable materials.
The glyoxal-phenolic condensates of this invention will typically have a percent by weight concentration of metal ions of less than about: 0.005% for sodium; 0.003% for calcium; 0.003% for iron; and 0.002% for potassium for a total concentration of such ions of less than about 0.013%.
The condensates of this invention can be used alone to cure epoxy resins but preferably they are used in combination with other epoxy resin curing agents such as a conventional phenolic novolac resin, e.g., one which does not have the high fluorescence values of this invention. Such other curing agent can comprise about 50% to 97% by weight of such curing composition and the glyoxal-phenolic condensate can comprise about 1% to 50% by weight of such curing composition. Preferably, the other curing agent can comprise from about 50% to 95% by weight of such curing composition and the glyoxal-phenolic condensate can comprise about 1% to 50% by weight of such curing composition. About 10 to 30 parts of this type of curing composition can be used to cure 100 parts of epoxy resin.
Compositions of this invention can contain, for each 100 parts of a conventional epoxy resin, i.e. which does not have the high fluorescence values of this invention, or simply resin, about 1 to 35 parts based on the weight of the epoxy resin, the inventive glyoxal-phenolic condensates, epoxidized derivatives thereof, and mixtures containing the condensates and epoxidized derivatives.
The preferred polyepoxide products of this invention when used in electronic applications such as laminates for the production of printed circuit boards will typically comprise the following composition based on 100 parts of an epoxy resin, e.g., an epoxy resin such as the diglycidyl ether of bisphenol A:
(a) about 10-30 parts of a curing agent such as a phenol-formaldehyde novolac;
(b) about 1 to 30 parts and preferably about 2-20 parts of a member selected from the group consisting of a glycidylated polyphenolic of this invention, a reaction product of an epoxy resin and a polyphenolic of this invention, a polyphenolic of this invention, and mixtures thereof; and
(c) optionally, an epoxy curing accelerator.
Epoxy resins useful in this invention can be conventional epoxy resins, i.e., those not containing the high fluorescent glyoxal-phenolic residue of this invention. Such resins can have WPE values of about 190 to about 10,000 and preferably about 190 to about 500. Illustrative of such conventional epoxy resins, or simply epoxy resins, there can be mentioned those of diglycidyl ether resins, such as those having the above mentioned WPE values, prepared by contacting a dihydroxy compound with an excess of epichlorohydrin in the presence of an alkali metal hydroxide wherein the dihydroxy compound can be: bisphenol A; brominated bisphenol A, particularly tetra brominated bisphenol A; bisphenol F; resorcinol; neopentyl glycol; cyclohexanedimethanol, and the like; and mixtures thereof. Such resins are also referred to as being based on or derived from the dihydroxy compound involved, e.g. bisphenol A. Also, such conventional epoxy resin can be that of: epoxy phenol novolacs; epoxy cresol novolacs; aromatic glycidyl amine resins such as tri glycidyl-p-amino phenol; N, N, Nxe2x80x2,Nxe2x80x2-tetraglycidyl-4, 4xe2x80x2-diaminodiphenyl methane; glycidyl ethers of a phenolic novolac; glycidyl ethers of an o-cresol/formaldehyde novolac; poly(glycidylated) copolymers of glycidyl methacrylate wherein the comonomer includes unsaturated compounds such as acrylates, methacrylates and styrene; and mixtures of the various conventional epoxy resins. Non-glycidylated epoxy resins may also be employed. Examples of such non-glycidylated epoxy resins include: limonene dioxide (weight per epoxy of 85); vinyl cyclohexene dioxide; divinyl benzene dioxide; 5-vinyl-2-norbornene dioxide (weight per epoxy of 76); 1,5-heptadiene dioxide; 1,7-octadiene dioxide. The non-glycidylated epoxy compounds are preferably used in conjunction with glycidylated epoxy resins and are also useful as diluents.
The conventional epoxy resin can be a flame retardant epoxy resin such as a halogenated epoxy resin, e.g., chlorinated or brominated epoxy resin. Illustrative of such brominated epoxy resins there can be mentioned the brominated product of the diglycidyl ether of bisphenol A, e.g., EPON 1124 (CAS No.: 26265-08-07) of Shell Chemical Co. Such brominated epoxy resins can be used in flame retardant compositions with other epoxy resins.
Preferred, non-conventional epoxy resins of this invention include: glycidylated polyphenolics of a phenol and glyoxal wherein the polyphenolic prior to glycidylation has a fluorescence which is at least 30% higher than Acridine Orange Base by the test method given herein or glycidylated polyphenolics of this invention having a fluorescence which is at least equal to that of Acridine Orange Base by the test method given hereinabove; and a reaction product of about 4 to 8 parts of a conventional glycidyl epoxy resin to each part of a polyphenolic of a phenol and glyoxal of this invention having a fluorescence which is at least 30% higher than Acridine Orange Base by the test method given hereinabove or such inventive reaction product having a fluorescence which is at east equal to Acridine Orange Base by the test method given hereinabove.
Epoxy curing accelerators can be used in a quantity sufficient to accelerate the cure of the epoxy resin. Generally, such quantity is from about 0.05 to 0.5 parts based on 100 parts of the epoxy resin and particularly about 0.1 to 0.2 parts. Such accelerators include 2-methylimidazole, 2-ethyl4-methylimidazole, amines such as 2,4,6-tris (dimethylaminomethyl)phenol and benzyldimethylamine, and organophosphorus compounds such as tributylphosphine and triphenylphosphine.
Reactive diluents may also be present to lower viscosity and improve handling characteristics. Examples of reactive diluents include neopentylglycol diglycidyl ether; butanediol diglycidyl ether; resorcinol diglycidyl ether; and cyclohexane dimethanol diglycidyl ether.
A variety of curing agents well known in the art can be used for the epoxy resin. They include but are not limited to aromatic amines, polyamidoamines; polyamides; dicyandiamide; phenol-formaldehyde novolacs; melamine-formaldehyde resins; melamine-phenol-formaldehyde resins; and benzoguanamine-phenol-formaldehyde resins.
When phenol novolacs are used as curing agents a catalyst (accelerator) i generally employed and may be selected from tertiary organic amines such as 2-alkylimidazoles; benzyldimethylamine; and phosphines such as triphenylphosphine and mixtures thereof.
The phenol novolac curing agents are condensation products of a phenol with an aldehyde or ketone wherein the phenol can be selected from phenol itself, cresols, xylenols, resorcinol, bisphenol-A, paraphenyl phenol, naphthol, and mixtures thereof. Substituents for the phenolic monomers include hydroxy, alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms as well as phenyl. Novolacs and dicyanodiamide are preferred curing agents. Particularly preferred curing agents are the phenol-formaldehyde novolacs and ortho-cresol-formaldehyde novolacs having a molecular weight of about 300 to 5,000 and preferably about 1,000 to 5,000. Illustrative of the aldehydes for preparation of the phenol novolac curing agents there can be mentioned formaldehyde, acetaldehyde, benzaldehyde and hydroxybenzaldehyde. Illustrative of ketones for preparation of the phenol novolac curing agents there can be mentioned acetone, hydroxyacetophenone, and methyl ethyl ketone.
A wide variety of solvents may be used in the compositions of this invention, including halogenated solvents, ketones, alcohols, glycol ethers, glycol acetates, N, N-dimethylformamide. The latter is particularly useful when dicyandiamide is used as curing agent. Ketones include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone.
The laminates of this invention will generally contain about 20% to 60% by weight of resinous matrix material and about 40% to 80% by weight of reinforcing material such as glass cloth.
The structure of the laminates of this invention are the same as those of conventional laminates containing a reinforcing agent such as glass cloth, and a resinous matrix comprising an epoxy resin and a curing agent for the epoxy agent such as a phenol-formaldehyde resin, except that the resinous matrix will also contain from about 1 to 35 parts by weight, preferably about 1 to 15 parts by weight, based on the weight of of the resinous matrix, of a glyoxal-phenolic condensate, residue or mixture thereof. The epoxy resin, curing agent, glyoxal-phenolic condensate or residue thereof and optionally a solvent system for the epoxy and curing agent, can comprise at least 40% by weight of the resinous matrix or mixture.
The resinous matrix of the laminates of this invention containing a solvent will generally contain, by weight, (1) from about 40 to 80 and preferably 50 to 70 parts of an epoxy resin; (2) about 1 to 15 parts of a condensate of this invention or an epoxidized residue of said condensate or mixture thereof; (3) about 10 to 35 and preferably 15 to 30 parts of a solvent; and about 7 to 35 parts of an epoxy curing agent. The epoxidized residue can be that of a glycidylated condensate (polyphenolic) of this invention or that of the reaction of 4 to 8 parts of an epoxy resin for each part of the condensate.
The laminates of this invention can be made flame retardant by conventional techniques such as: (a) the use of a halogenated epoxy resin as the main resin matrix ingredient; (b) a brominated or chlorinated flame retardant additive such as chlorinated bisphenol-A, tetrabrominated bisphenol-A or tris(2,3-dibromopropyl)phosphate; or (c) the use of a non-halogenated flame retardant such as a nitrogen containing resin such as a triazine, e.g., a melamine-formaldehyde resin, a melamine-phenol-formaldehyde resin, a melamine-benzoguanamine-phenol-formaldehyde resin or a benzoguanamine-phenol-formaldehyde resin. The nitrogen containing curatives are preferably used together with a phosphorus containing material. Illustrative of the phosphorus containing material there can be mentioned organic and inorganic phosphorus containing materials such as: aryl phosphates and phosphites such as the trade named product PHOSFLEX 580 of Akzo-Nobel; triarylphosphines such as triphenylphosphine; triarylphosphorus oxides such as triphenylphosphorus oxide; alkyl-aryl phosphites such as the trade named products ULTRANOX 626 and WESTON PNPG, both from GE Specialty Plastics; ammonium phosphates; red phosphorus; and mixtures thereof. The phosphorus containing materials can be employed at levels of about 2% to 15% based on 100 parts of the primary epoxy resin. By the term primary epoxy resin is meant the conventional or epoxy resin which is not prepared from a glyoxal-phenolic condensate of this invention.
The epoxy resin used in the laminate compositions of this invention will have a weight per epoxide (WPE) value of from about 190 to 10,000 and preferably from about 190 to 500. The epoxy resins for laminating and coating formulations are generally solvent based. Coating formulations may include fillers whereas laminating formulations generally impregnate multiple layers of a fiber matrix such a glass cloth with a phenolic compatible finish.
The laminate can be prepared at room temperature or by heating under pressure a layer comprising at least one sheet of prepreg comprising an epoxy resin as impregnate. The pressure used in making the laminates can vary from the contact pressure of applying a laminated lining to a tank wall to the high pressure, e.g., 1,000 psi or more, used in the manufacture of electrical insulation sheets. The temperature used in making the laminates can vary over a wide range such as that of about room temperature to over 210xc2x0 C. The use of a solvent in the laminate compositions is optional. Conventional laminating techniques can be used in making the laminates of his invention such as the wet or dry-lay-up techniques.
Reinforcing fibers or fabrics of reinforcing fibers for use in laminates include glass fibers and mats; carbon and graphite fibers, cellulosic paper, fibrous polyamide sheets, fibrous quartz sheets, woven fibrous glass cloth, unwoven fibrous glass mat, and the like. Fillers such as quartz powdered, mica, talc, calcium carbonate and the like may also be added to the resinous matrix in the laminate.
The weight average molecular weight (Mw) and number average molecular weight(Mn) herein are measured using gel permeation chromatography and phenolic compounds and polystyrene standards. The sample molecular weight to be measured is prepared as follows: the sample is dissolved in tetrahydrofuran and the solution is run through a gel permeation chromatograph. Any free phenolic in the sample is excluded from calculation of molecular weight.
xe2x80x9cViscosity, cps at 175xc2x0 C.xe2x80x9d or xe2x80x9cCandP, cps (175xc2x0 C.)xe2x80x9d is the viscosity in centipoises as measured by cone and plate melt viscosity using a No. 40 cone.
The quantity of TPE in the various reaction mixtures was determined by the following method.
(a) The reagents used were para-ethyl phenol, TPE, and silylation reagent.
(b) Procedure for determining TPE was as follows:
A silylation reagent was prepared as follows: into 25 ml (milliliter) reaction flask, add by syringe: 10 cc (cubic centimeters) of pyridine, 3 cc of trimethylchlorosilane (TMCS), and 10 cc of hexamethyldisilazane (HMDS). This was left to stand for 5 to 10 minutes.
(c) The TPE standard solution is prepared as follows:
Weigh into vial (appropriate for silylation) approximately 30 mg each TPE and p-ethylphenol. Add 1 cc silylation reagent. Shake until dissolved (approximately 10 minutes). Heat in low temperature oven overnight. Inject 1 microliter into gas chromatograph. Use methyl ethyl ketone as rinses. The column used for this analysis is Dexsil 300 which is supplied by Supelco of Belfonte, Pa.
In order that those skilled in the art may more fully understand the invention presented herein, the following examples are set forth. All parts and percentages in the examples, as well as elsewhere in this application are by weight, unless otherwise specifically stated.